A number of test systems has been developed in our laboratory for evaluating drugs potentially useful in human cancer of the prostate. The systems have relied on unique features of the prostate and include the following: 1) the effects on 5 alpha-reductase and arginase activity in the rat prostate; 2) the effects on the deposition of labeled androgens and estrogens in the dog and baboon prostates; 3) the incorporation and distribution of labeled zinc in the rat and baboon prostates; and 4) the development of an organ culture system utilizing animal and human prostate explants and the effects of various chemotherapeutic drugs on the parameters listed above in such explants of the prostatic tissue in organ culture. Our ultimate aim is not only to expand the testing of the effects to a large group of new and "old" anti-cancer agents, but also to establish conditions for organ culture of explants of human prostatic cancer. The latter approach would afford a direct evaluation of the effects of drugs on cancers of varying histology and drug-sensitivity.